This invention relates in general to drive train systems for transferring rotational power from a source of rotational power to a rotatably driven device. In particular, this invention relates to an improved method for rotatably balancing a driveshaft adapted for use in such a vehicular drive train system for transferring rotational power from an engine/transmission assembly to an axle assembly.
Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the source to a rotatably driven mechanism. For example, in most land vehicles in use is today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
Ideally, the driveshaft tube would be formed in the shape of a cylinder that is absolutely round, absolutely straight, and has an absolutely uniform wall thickness. Such a perfectly shaped driveshaft tube would be precisely balanced for rotation and, therefore, would not generate any undesirable noise or vibration during use. In actual practice, however, the driveshaft tube and other components of the driveshaft assembly usually contain variations in roundness, straightness, and wall thickness that result in minor imbalances when rotated at high speeds. To prevent such imbalances from generating undesirable noise or vibration when rotated during use, therefore, it is commonplace to counteract such imbalances by securing balance weights to selected portions of the driveshaft tube or other components of the driveshaft assembly. The balance weights are sized and positioned to counterbalance the imbalances of the driveshaft assembly such that it is balanced for rotation during use.
Traditionally, the balancing process has been performed with the use of a conventional balancing machine. A typical balancing machine includes a pair of fittings that are adapted to support the ends of the driveshaft assembly thereon. The balancing machine further includes a motor for rotating the driveshaft assembly at a predetermined speed. As the driveshaft assembly is rotated, the balancing machine senses vibrations that are caused by imbalances in the structure of the driveshaft assembly. The balancing machine is responsive to such vibrations for determining the size and location of one or more balance weights that, if secured to the driveshaft assembly, will minimize these imbalances. The rotation of the driveshaft assembly is then stopped to allow such balance weights to be secured to the outer surface of the driveshaft tube or other components of the driveshaft assembly in a conventional manner, such as by welding, adhesives, and the like. The driveshaft assembly is again rotated to confirm whether proper balance has been achieved or to determine if additional balance weights are required. A number of such balancing machines of this general structure and method of operation are known in the art.
Although such prior art balancing machines have been effective, this balancing process has been found to be relatively slow and inefficient. This is because each driveshaft tube must usually be rotated and measured at least two times, a first time to measure the imbalances and determine the size and location of the balance weights, and a second time to confirm that proper balance has been achieved after the balance weights have been secured thereto. This time consuming process is particularly problematic in the context of balancing vehicular driveshaft tube, which are typically manufactured in relatively large volumes. Additionally, the costs associated with obtaining and maintaining such prior art balancing machines, and to provide the skilled personnel necessary to operate same, are relatively high. Thus, it would be desirable to provide an improved method for quickly and inexpensively balancing an article, such a driveshaft tube for use in a vehicular driveshaft assembly, for rotation about an axis.
This invention relates to an improved method for quickly and inexpensively balancing an article, such a driveshaft tube for use in a vehicular driveshaft assembly, for rotation about an axis. Initially, a balancing structure is provided that includes a chamber that contains a quantity of a first component of a balancing material. The balancing structure is secured to the article. Then, a quantity of a second component of the balancing material is disposed within the chamber so as to initiate solidification of the balancing material. Lastly, before the balancing material solidifies, the article and the balancing structure are rotated so as to cause the balancing material to move within the chamber to a position wherein the combined assembly of the article and the balancing structure are balanced for rotation. The balancing material solidifies in this position, thus permanently balancing the article for rotation.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.